Identification of textiles and fibres

Textile fibres from upholstery or embroidered panels, and fibres from leather-covered furniture, paper decorations, papier mâché and cardboard furniture can be examined under low power magnification for their structure and pattern, or microscopically for composition and origin. A 10X lens with a scale, for example, is useful in examining and counting the warp and weft threads, and for examining their condition (Adrosko, 1990; Emery, 1980). Upholstery conservators use a hand-lens, or binocular microscope in examining the nail pattern, and textile fragments of upholstery on the furniture, in order to discriminate original from later interventions (Francis, 1990; Howlett, 1990).

Fibres can be examined longitudinally and in cross-section to determine their composition and possibly their origin. For example, longitudinal sections of wool in good condition show characteristic scales covering the central cortex. On degraded wool fibres the scales may be worn away. Cotton fibres are twisted with frequent changes in direction. In transverse section, a cotton fibre is a collapsed hollow tube. Flax shows bundles of polygonal cells. Procedures are described by the American Association of Textile Chemists and Colourists (Weaver, 1984; Farnfield et al. (1985) and by Timar-Balazsy and Eastop (1998). Excellent descriptions are also given by Appleyard (1978), Howlett (1990), King (1985) and Catling and Grayson (1982). Fibres can also be examined for additives and finishes. Techniques for sample preparation are mentioned by Annis et al. (1992a, 1992b), Farnfield et al. (1985), Florian et al. (1990), King (1985), Weaver (1984) and Timar-Balazsy and Eastop (1998). The type of microscope required for fibre identification is similar to that needed for wood identification (McCrone, 1987; Weaver, 1984). A polarized light microscope with bright field and dark field illumination is recommended. A hot-stage for observing melting points of synthetic fibres is useful (Farnfield et al., 1985). Cross-sections can be cut by hand or on a microtome; good results have been obtained by Annis et al. (1992b) with a plate style microtome. Excellent results have also been achieved by embedding the fibre sample in a resin block before cutting the cross section (Rogerson, 1997).

Fibres can be identified using simple methods such as burning tests and wet chemical tests (Burnham, 1982; Emery, 1980; Roff and Scott, 1971; Timar-Balazsy and Eastop, 1998). For example, when held over a naked flame, protein fibres will curl away from the flame and will produce a smell of burning hair, rendering a black brittle ash. Cellulosic fibres smell of burnt paper and render a soft grey ash when burned.

Textiles can be examined by eye or under low magnifications to determine their spun structure (twist/ply), weight (thread count) and technique (weave, knit) This serves as an aid to identification of a particular textile and as a guide to what may need to be considered in treatment. Sophisticated methods like X-ray diffraction, or pyrolysis gas chromatography, can be useful in further identification of textiles or textile blends (Farnfield et al., 1985; Hardin and Wang, 1989). DNA mapping may prove to be invaluable in analyses of organic material (Paabo, 19931.

Some finishes, such as calendaring, are physical and may be detected by visual examination alone under low magnification. Chemical finishes may be detected by various wet chemical tests. The Beilstein test may be used as a simple means of screening organic and polymeric materials for the presence of chlorine (CCI, 1988a). The diphenylamine spot test can be used for cellulose nitrate (CCI, 1988b) and the amido black test for protein dressings (Martin, 1977). Further tests are described by Champion (1987), Martin (1977) and Timar-Balazsy (1998).

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